education series

Education Series – Gather ’round the Oak Barrel – Part 3

Our oak barrel story started in the forest then led us to the cooperage, and now it has led us to the bottle. After the barrel has gone through what can sometimes be a long creation process, it is time to fill it with wine. The topic of today’s post is what happens to that delicious wine while it is aging in the barrel. 


The amount of time that a wine can spend in a barrel can vary drastically from months to several years. There are several factors that can influence how long a wine might be oak aged. The main factors are the grape itself (longer time for more hearty red varietals and shorter time for thinner skinned reds and whites), the age of the barrel (barrels that have been used several times will not impart the same amount of flavor as fresh barrels), the region that the wine is made (in some wine regions there are regulations around how long a wine type must spend in oak), and ultimately the experience of the winemaker taking into account all of the above will determine how long a wine spends aging in barrel.


Regardless of the time that the wine spends in the barrel, there are few things that can be happening to the juice.  One thing that happens is the softening of the wine  that is due to the minute amount of oxygen that seeps in through the staves, causing a more rapid ( but still fairly slow) binding of the tannins versus the wines being in an air tight container. The oak itself imparts its own flavors and aromas into the wine. Besides the obvious wood and tea flavors that come from the wood, vanilla (most commonly from American oak), clove, smoky and caramel aromas/flavors (as well as others) can come from the barrel maturation.  Interestingly, the chemicals that provide the caramel aroma are generated during the toasting process. Two of these Maltol and Cyclotene have been shown to be flavor “accentuators”, helping to increase the presence of other flavors.  This is similar to the role that MSG plays in many food products. The last role of the oak barrel that I will mention that some say is the most important, is its natural ability to clarify and stabilize the wine, decreasing and or removing the need for fining and filtering the wine. Now this list was in no particular order of importance nor is it an exhaustive list of what oak does to the wine, although it is pretty complete. 

There are some great books out there than can go into great detail of the chemical reactions that are occurring inside a barrel that if you are a chemist can be quite fascinating.This completes the series on oak barrels. For the most part this has been pretty top level information on the process.  If anyone has questions I will be happy to try and answer them or if anyone just wants to discuss what is currently going on the barrel market, just shoot me an email.

 ReferencesOxford Companion to Wine, 3rd Edition, Jancis Robinson and The Wine Bible, Karen MacNeil

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Education Series – Gather ‘round the Oak Barrel – Part 2

In part 2 of this oak barrel trilogy I will be discussing the cooperage process, which is the process of making the barrels themselves.You may recall from part 1 that this whole process starts in the forest. Coopers (those individuals who make barrels) have historically utilized wood from the region that they are familiar with, meaning that American Coopers made barrels from American oak and French from French oak, and so on. This is not the case anymore; both French and American oak is being shipped across the pond to Coopers in either country.

The first step of barrel creation is the creation of the staves, which are the slats or boards that form the sides of the barrel. Although the staves can be sawed, the preferred method is to split the wood by hand or by machine to help preserve as much of the natural wood grain as possible. Keeping the grain of the wood intact is crucial to making water-tight barrels. After the staves are shaped, they are stacked together and typically set outside to age in the elements, as wood normally would. Sometimes to quicken the process, the staves are dried in a kiln prior to being set out to age. This entire process can take up to several years. Once the staves are properly aged, they are shaped, notched, and beveled and then finally ready for inspection.


image credit:

After the coopers have okayed the staves for barrel assembly, they start piecing them together to form the shape of a barrel. The staves are placed one by one inside of metal hoops (the chime hoop is first, then the quarter hoop, and then the bulge hoop; see picture) a process which the French call “mise en rose”, or “raising the barrel.” The phrase literally means “setting the rose,” most likely because unbent staves in the first hoop look like an open flower. The next step is to shape the barrel and set the 3 final hoops. This process is done by bending the wood staves via fire, water or steam. These methods soften the wood enough so that it can be bent and molded into the perfect shape, as well as allow for the three remaining rings to be riveted into place.

image from Winebusiness.comThe next step in the process is toasting the inside of the barrel. This process is sometimes done simultaneously with the heating of the staves for shaping, and sometimes may not be done at all. Barrels can be toasted using a variety of different heat sources. Whether it be gas fire, burning oak chips, convection, etc. the end result is that interior of the barrel staves are toasted to a specified level. Winemakers can specify ahead of time how “toasty” they want there barrel to be, from light to heavy toast. To achieve the varying toast levels, coopers use different time and temperature equations, developed through years of personal experience. Technology has helped in this process, as sensors can be placed inside of the barrels to know when the desired level of char has been achieved. In Part 3 of this series I will talk about how the varying toast levels affect wine flavor.

The final step is the shaping and fitting of the barrel head. Larger staves are cut and bound together and then shaped to fit snuggly into the end of each barrel in grooves called crozes. Barrel heads are usually left un-toasted.

Actually the final final step is the branding of each barrel with the Cooperage house’s logo on the head of each barrel. Sometimes wineries pay to have their name burned into the head as well.

Again, I will give my disclaimer that this is a primer into the barrel making process. The process for making an oak barrel for wine or other spirit is a great skill and coopers apprentice for years before they are allowed to shape and toast the barrels themselves. Although this process is being done more and more by machine in order to make barrels cheaper (though not by much), there are still a lot of cooperages that do most of the work by hand.

Here are some links to cooperages that can give you more information into this really fascinating process.

World Cooperage


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Education Series – What are Tannins?


A while ago I said I was going to start a wine education series. As you may have noticed, I didn’t get very far with that idea– I think I did only one entry on malolactic fermentation. So I am recommitting myself to this effort through Education Tuesdays. Every Tuesday I will post on a topic, term, or subject that I think needs to be more talked about or better explained.

To start off the series, today’s bit is on tannins. The term tannin is used a lot when describing a wine, whether it is to talk about the mouthfeel (soft, harsh, firm, gripping, etc.) or to determine it’s aging ability. So what is a tannin?

The technical definition for a tannin is a plant-based polyphenol that binds and precipitates proteins, and is found in grapes skins, seeds and stems as well teas, and other fruits and plants. The name “tannin” is actually derived from the tanning process of animal hides.  The non-technical answer is that tannins are the substance in wine that makes your mouth feel dry and if too pronounced, can provide a bitter taste.  If tannins are excessive as they might be in a young wine, it feels like someone sucked all the moisture out of your mouth. If the wine has been aged, or did not have prolonged contact with the skins, the tannins will be much softer and give you what is described sometimes as a velvety feel in the mouth.

Other than the skin and seed contact that can give red wine its tannic structure, oak and other wood barrels that red wine is commonly aged in can provide some tannins as well.

I mentioned that tannins can be reduced over time with aging, and that pronounced tannins in a particular wine can relate to its ability to age well (in addition to fruit, acid and alcohol levels). So how does this work? What are the tannins doing in that bottle of wine over time?

First, the reason that the wine has better age ability with increased tannins is due to the chemical’s natural preservative effects. Second, the reason that wines taste less tannic and feel less harsh over time is that the tannins gradually polymerize (fancy word for join up) and when joined together in long chains give a much softer mouthfeel.

This was a bit of a technical description but was more in my terms, so I hope it made sense. If you have more questions about tannins or need some more clarification please shoot me an email.

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